Although substantially transparent and colorless block copolymers have been prepared by a variety of initiator and monomer charge sequences, some of the prior art materials such as described in U.S. Pat. No. 4,080,407 are not entirely satisfactory in regard to impact strength and craze-resistance. Articles fabricated from some of the available block copolymers are quite satisfactory in regard to exhibiting low blueness and a high degree of transparency. However, these articles may also exhibit somewhat low impact strength and a tendency to craze on being impacted.
Such deficiencies of available block copolymers are evident in packaging applications such as blister packs for bandages and syringes. These transparent colorless packs are intended to display and protect the contents and maintain a sterile atmosphere within the pack. Crazing of these packs due to squeezing during shipping is very undesirable because the crazed packs and their contents are discarded on the presumption that the sterile atmosphere within the pack has been contaminated by an air leak.
Thus, there is a need for block copolymers which possess the capacity to impart good impact strength and craze-resistance to transparent colorless manufactured articles, particularly in the packaging field.